With the development of display technology and progress of the society, liquid crystal display technology is being more and more widely applied by people, playing very important roles in industrial production and people's lives.
An alignment film that keeps liquid crystal molecules in a particular orientation in the case where there is no effective electric field is generally prepared by two methods: rubbing alignment method and photo alignment method. The rubbing alignment method had been widely used by display panel manufacturers. Rubbing alignment method uses a lint roller to rub a surface of a film-to-be-aligned, such that the molecules on the surface of the film-to-be-aligned are arranged in a particular direction. However, when the roller rubs the film-to-be-aligned, dust particles and electrostatic residues may be easily generated, affecting the yield of the product. Therefore currently photo alignment method is commonly employed to align the film-to-be-aligned.
Photo alignment method utilizes polarized light, produced by ultra-violet (UV) light passing through a polarizer, to illuminate a film-to-be-aligned on a substrate, thereby aligning the film-to-be-aligned, and causing the surface of the film-to-be-aligned to have optical anisotropy. Photo alignment method can improve yield of the product and stability of production equipment.
But during the alignment by UV polarized light, photo alignment method would result in incomplete curing of film-to-be-aligned if the temperature is too low. If the temperature is too high, then it will cause damage to the film-to-be-aligned, and alignment disorder of the liquid crystal may occur, resulting in alignment defects such as bright spots appearing on the liquid crystal panel at the time of display. Thus temperature control during photo alignment has become critical to photo alignment technology, while a conventional photo alignment apparatus is not able to implement supervision on the temperature during photo alignment.